Variation in Formula Supplementation of Breastfed Newborn Infants in New York Hospitals

Abstract

OBJECTIVES: We examined the variation between 126 New York hospitals in formula supplementation among breastfed infants after adjusting for socioeconomic, maternal, and infant factors and stratifying by level of perinatal care.

RESULTS: Formula supplementation percentages varied widely among hospitals, from 2.3% to 98.3%, and was lower among level 1 hospitals (18.2%) than higher-level hospitals (50.6%–57.0%). Significant disparities in supplementation were noted for race and ethnicity (adjusted odds ratios [aORs] were 1.54–2.05 for African Americans, 1.85–2.74 for Asian Americans, and 1.25–2.16 for Hispanics, compared with whites), maternal education (aORs were 2.01–2.95 for ≤12th grade, 1.74–1.85 for high school or general education development, and 1.18–1.28 for some college or a college degree, compared with a Master’s degree), and insurance coverage (aOR was 1.27–1.60 for Medicaid insurance versus other). Formula supplementation was higher among mothers who smoked, had a cesarean delivery, or diabetes. At all 4 levels of perinatal care, there were exemplar hospitals that met the HealthyPeople 2020 supplementation goal of ≤14.2%. After adjusting for individual risk factors, the hospital-specific, risk-adjusted supplemental formula percentages still revealed a wide variation.

What’s Known on This Subject:

Nonmedically indicated formula supplementation has been shown to adversely impact exclusive breastfeeding and is associated with shorter duration of breastfeeding. A number of maternal and infant factors are associated with formula supplementation; their prevalence varies across hospitals in New York.

What This Study Adds:

Formula supplementation of breastfed infants varies across hospitals. Much of this variation persists even after adjusting for maternal and infant factors. Hospital breastfeeding policies and supplementation practices contribute to this variation. Improving hospital practices could lead to improved breastfeeding outcomes.

Exclusive breastfeeding for the first 6 months, with continued human breast milk feeding through 12 months or longer, is recommended to provide optimal infant and maternal health benefits.1,2 Maternity care provided during birth hospitalization has been shown to directly impact breastfeeding success. The Ten Steps to Successful Breastfeeding (Ten Steps), individually or combined, have been associated with reduced formula supplementation, increased exclusive breastfeeding, and longer breastfeeding duration through at least 8 weeks of age.3 Implementation of the Ten Steps by hospital maternity services is widely recommended,2,4 and forms the basis for the Baby-Friendly Hospital initiative.5 Step 6 (not providing supplemental formula to healthy breastfed infants unless medically indicated) is the step most predictive of breastfeeding success.6 However, only 26% of US hospitals report having implemented Step 6.7 Although there is no US benchmark for formula supplementation of breastfed infants during birth hospitalization, the HealthyPeople 2020 (HP2020) objective MICH-23, which is to reduce the proportion of breastfed newborns who receive formula supplementation within the first 2 days of life to no more than 14.2%, seems applicable.8 Because US insurance carriers are required to cover 48 hours of newborn care, most infants spend the first 2 days in the hospital. Whether this objective is met is highly dependent on the hospital’s maternity care policies and practices.7,9 New York, compared with other US states, has the second-highest proportion of mothers who report that their breastfed infant received formula before 2 days of age (26.1%). This is much higher than the national average (17.1%).10 It is unlikely that infants in New York are at increased medical risk and have a medical indication for formula supplementation.

Many women (68%) report not meeting their own breastfeeding goals during birth hospitalization or after discharge.11 One of the most common disappointments expressed by new mothers is their inability to exclusively breastfeed during birth hospitalization because their newborn was fed formula.12 Maternal factors, infant health status, and hospital maternity care, including timing and duration of mother-infant skin-to-skin bonding, timing of the first breastfeeding, and duration of mother-infant rooming-in, are important determinants in whether the newborn receives supplemental formula.13 Disparities in breastfeeding by race, ethnicity, and socioeconomic status (SES) have also been reported.14 Although variation among hospitals in formula supplementation of breastfed newborn infants has been reported in New York and California,15,16 there is no formal, published study in which the researchers evaluate the variation across hospitals in formula supplementation or control for individual factors known to impact breastfeeding, such as SES or maternal or infant risk factors.

Our purpose in this study is to measure (1) the variation across hospitals in formula supplementation of breastfed newborn infants; (2) the impact of socioeconomic, maternal, and infant factors on formula supplementation; and (3) the variation in formula supplementation across hospitals after adjustment for these risk factors.

Methods

Study Population

All infants born alive during 2014 in 126 New York hospitals that provide maternity services were eligible to be included in the study. Infants were excluded for the following reasons: (1) they were admitted to the NICU, (2) transferred between hospitals, (3) received an unknown method of feeding, (4) were not fed any breast milk during birth hospitalization, (5) had a gestational age that was unknown or <37 weeks’ gestation, (6) had an unknown or low birth weight (ie, <2500 g), or (7) were the product of a multiple birth (Fig 1; N = 160 911).

Determination of study population, New York state (NYS), 2014.The flow diagram illustrates the selection of the final population and the study population in models. Excluded mother-infant dyads may have met more than 1 exclusion criterion. (Data Source: 2014 New York Statewide Perinatal Data System).

Study Variables

The outcome of interest (dependent variable) was defined as an infant who was fed both breast milk and formula (formula supplementation). Independent variables included maternal SES and maternal and infant risk factors such as race and ethnicity, educational attainment, marital status, primary payer, maternal age group, prepregnancy weight status, prepregnancy or gestation hypertension, prepregnancy or gestational diabetes, smoking before or during pregnancy, late care or no perinatal care, first live birth, and cesarean delivery. Maternal prepregnancy BMI was calculated on the basis of prepregnancy weight and height.

In New York, perinatal care is regionalized to provide the full range of perinatal services in a geographic area. There are 4 hierarchical levels of perinatal care. Level 1 hospitals provide care to low-risk pregnant women and newborns; they do not operate NICUs. Level 2 hospitals provide care to moderate-risk women and newborns. Level 3 hospitals provide complex care. The regional perinatal center (RPC) hospitals provide the most sophisticated care in the region for specialized consultation on complicated cases. Each RPC also provides support, training, and quality improvement services to the affiliated hospitals within their region, and ensures timely transfer of patients to higher-level perinatal hospitals within the region. For level 2, level 3, and RPC hospitals, the number of births and intensity of neonatal care must meet minimum volume standards during each calendar year.17

Statistical Analysis

Bivariate analysis: We determined the formula supplementation percentages for the total study population and each independent variable. χ2 tests were conducted to assess the unadjusted association of formula supplementation with each of the independent variables.

We conducted multivariable hierarchical logistic regression modeling separately for each level of perinatal care to account for any unmeasured differences in hospital policies or practices at each level. Independent variables for mother-infant dyads were entered as fixed-effect components, and the hospital identifier was entered as a random intercept component.18

A full model was fit with all independent variables described above. Model selection for the fixed effects were performed by using backward elimination with preference given to models with lower Akaike information criterion.19 For each perinatal level, the final model with the lowest Akaike information criterion was used to estimate the adjusted odds ratios (aORs) (95% confidence intervals [CIs]) for formula supplementation. The final models only included variables with a P value <.2.

We calculated the observed percentage of formula supplementation for each hospital and each perinatal care level. Hospital-specific predicted and expected formula supplementation percentages were determined from the final model for each perinatal care level.18 The risk-adjusted formula supplementation percentage for each hospital was calculated by multiplying the hospital-specific ratio for formula supplementation (predicted percentage divided by expected percentage) by the observed formula supplementation percentage for the corresponding perinatal care level.18

We compared the between-hospital variances for models of supplemental feeding before and after risk adjustment and calculated the IntraClass coefficient and the proportional change in variances.20,21 The predictive accuracy of the models was assessed by the area under receiver operating characteristic curve. SAS version 9.4 was used for all analyses. P values <.05 were considered statistically significant.

The study was approved by the New York State Department of Health Institutional Review Board.

Distribution of Study Variables by Formula Supplementation, New York State, 2014

Before adjustment, all independent variables were statistically associated with formula supplementation (Table 1, all P values <.001). Of note, infants whose mother did not smoke before or during pregnancy, compared with mothers who smoked, were more likely to be supplemented with formula.

We show in Table 2 the aORs for the associations between formula supplementation with the independent variables from the final model for each perinatal care level. Newborn infants whose mothers were non-Hispanic African American, Asian American, or Hispanic were more likely to receive formula supplementation compared with non-Hispanic white mothers. Asian American infants were at the highest risk of receiving supplemental formula at all perinatal care levels. The aORs for mothers who were non-Hispanic other race were also significantly higher at level 1, 2, or 3 hospitals. The strength of associations for race and ethnicity varied by the level of perinatal care, with stronger associations seen at lower-level hospitals. There was a strong, consistent inverse relationship with maternal educational attainment and formula supplementation at all 4 perinatal care levels (Table 2). The aORs were also higher for mothers with Medicaid insurance (a marker for low income) and who were not married.

Odds of Formula Supplementation by Hospital Level of Perinatal Care, Adjusted for Sociodemographic, Health, and Other Factors, New York State, 2014 (N = 154 583)

At all perinatal levels, increasing maternal weight status was associated with increasing odds that the infant received formula supplementation after adjusting for socioeconomic, maternal, and infant risk factors, a finding that was not observed in the unadjusted results (Table 1). Newborns whose mothers smoked were at higher odds for formula supplementation, which is opposite from the unadjusted results. Newborns whose mothers had diabetes or hypertension were more likely to receive supplemental formula compared with newborns whose mothers did not have these conditions. Infants born by cesarean delivery or were not the first child also had higher odds for formula supplementation at all levels of perinatal care.

The observed (unadjusted) formula supplementation percentages varied widely across hospitals, from 2.3% to 98.3% (Fig 2). The average supplementation percentages for level 1, level 2, level 3, and RPC hospitals were 17.7%, 51.7%, 51.2%, and 56.7%, respectively (Fig 2). At each perinatal care level, there were exemplar hospitals that met the HP2020 target of ≤14.2%. The proportion of hospitals meeting this objective, however, was much higher among level 1 hospitals (55%, N = 27) compared with level 2 (4%, N = 1), level 3 (12%, N = 4), or RPC hospitals (6%, N = 1). In 2014, 7 New York hospitals were designated as Baby-Friendly. Among the higher-level perinatal hospitals, 4 of the 6 exemplar hospitals were designated as Baby-Friendly (level 2 [1 out of 1], level 3 [2 out of 4], and RPC hospitals [1 out of 1]), but none of the exemplar level 1 hospitals were designated as Baby-Friendly (0 out of 27) (Fig 2).

Hospital observed and adjusted formula supplementation percentage by level of perinatal care, New York state, 2014. Each square represents the observed percentage of formula supplementation for a Baby-Friendly hospital, and the cross represents the hospital’s corresponding risk-adjusted percentage of formula supplementation. Each triangle represents the observed percentage of formula supplementation for a specific hospital (not Baby-Friendly hospital) and the circle represents the hospital’s corresponding risk-adjusted percentage of formula supplementation. The pink horizontal line shows the average percentage of formula supplementation for each perinatal care level, and the green dash line shows the HP2020 objective of formula supplementation rate.

We show in Table 3 the between-hospital variance results, which are consistent with the patterns seen in Fig 2. Before statistical adjustment for any risk factors, level 3 hospitals had the largest variation in formula supplementation (48%), followed by level 2, RPC, and level 1 hospitals (34%, 28%, and 15%, respectively). Risk adjustment had the greatest impact in reducing the variance in level 2 hospitals (by ∼18%), primarily because of socioeconomic factors.

Between-Hospital Variance of Formula Supplementation in the Null Model, SES Model, and the Final Model

Discussion

In this study, we confirm previous findings that formula supplementation varies by multiple sociodemographic and maternal and infant risk factors, and that race and/or ethnicity and low educational attainment are 2 of the strongest determiants.12,22–24 Researchers in an earlier study found a large variation among hospitals in the percentages of newborn infants who were exclusively breastfed, after adjusting for some mother and infant characteristics.25 We are the first, however, to risk-adjust hospital-specific rates of formula supplementation for the many socioeconomic and patient factors known to impact breastfeeding. After doing so, we found that most of the hospital variation in formula supplementation of breastfed infants persisted. Researchers in previous studies have found that breastfeeding initiation and exclusive breastfeeding rates differed between hospitals, and that these percentages were related in a dose-response manner with the number of recommended hospital maternity practices (ie, Ten Steps) received by the mother.13

Most women decide whether to breastfeed before delivery,26 and these planned intentions to breastfeed are associated with both initiation and duration of breastfeeding.27–29 Intention to breastfeed by itself, however, is only one factor. Researchers conducting a study of mothers found that social support and subjective norms were important enabling factors that determined continued breastfeeding at 1 month.30 Among women who intended to exclusively breastfeed for several months, 68% reported they did not meet their own breastfeeding goals.11

Formula supplementation during birth hospitalization can be a contributing factor, interfering with exclusive breastfeeding as well as being associated with shorter duration of breastfeeding. The provision of supplemental formula (when not medically indicated) may undermine a mother’s intention to exclusively breastfeed, leading to feelings of frustration, powerlessness, and a sense of failure.31 It can provide a conflicting message that may be interpreted as the hospital staff or providers promoting formula feeding for healthy infants.32

Hospital staff report that one of the most common reasons for in-hospital formula supplementation is the mother’s request.33 Whether the variation in formula supplementation by race and/or ethnicity or income reflects variation in maternal requests for formula by race and/or ethnicity or SES factors is not known. Increased formula supplementation of breastfed infants was observed among families on Medicaid, with higher odds at higher-care level perinatal hospitals. The reasons for this are not known, but researchers in other studies suggest that factors such as not participating in prenatal classes or distributing gift bags with free formula at discharge increase formula supplementation.34 A mother’s request for formula is often due to inadequate preparation for newborn care, lack of knowledge about breastfeeding, or a belief that formula was the solution for perceived breastfeeding problems.33,34 Researchers of a previous study in New York showed that the ratio of professional lactation consultants per 1000 births was lower at higher-level perinatal hospitals.35 Therefore, on-site lactation support for new mothers may be less in higher-level hospitals. In addition, the authors of a study of African American women found that they were more likely to encounter unsupportive cultural norms, such as perceptions that breastfeeding is inferior to formula feeding and lack of partner support.36 The levels of social support, cultural norms, and beliefs around breastfeeding may contribute to the high supplementation rate and disparities in breastfeeding.37

Researchers in numerous studies have found that the specific hospital maternity care a woman receives is related to her breastfeeding success,38,39 and that the numbers of the recommended policies and practices present correlates with hospital-specific breastfeeding initiation and exclusivity rates.13 Women who deliver at hospitals that implement Baby-Friendly policies and become designated as Baby-Friendly have higher breastfeeding initiation rates and longer breastfeeding duration.40,41

In New York, no level 1 hospitals were designated as Baby-Friendly (ie, none met the certification criteria that they have implemented the Ten Steps42 and the International Code of Marketing of Breast-milk Substitutes43).44 However, 55% (N = 27) of level 1 hospitals had low supplementation rates. In contrast, among the higher-level perinatal hospitals, in which the average supplementation rate is higher and the variability greater, there were exemplar hospitals, and 4 of the 6 exemplar hospitals were designated as Baby-Friendly. However, among the 7 Baby-Friendly designated hospitals, 3 did not have low supplementation rates (ie, ≤14.2%). Thus, being designated Baby-Friendly is not sufficient to ensure that a hospital has a low supplementation rate. Prenatal breastfeeding education, health care provider and staff training, lactation support, social support, and peer counseling are also related to breastfeeding outcomes.45–47

Research into these exemplar hospitals by using community-based participatory methodology and/or a positive deviance approach might provide insight into important but hitherto undocumented maternal behaviors, family characteristics, staff or community attitudes, and cultural determinants (beyond the recognized hospital policies and practices and socioeconomic, infant, and maternal factors) that are contributing to their better breastfeeding outcomes.48,49 Recent community-based efforts, sensitive to the cultural determinants and focused on changing social norms, are proving to be successful in improving breastfeeding rates, particularly in disadvantaged communities.50,51

The finding that formula supplementation is much lower (30%–40%) at level 1 hospitals compared with level 2, level 3, or RPC hospitals is striking. A notable difference between level 1 hospitals and the higher-level hospitals is that level 1 hospitals do not have an NICU. This might contribute to differences in the hospital breastfeeding culture, such that formula feeding, which is more prevalent at higher-level perinatal hospitals, is viewed as more acceptable by hospital staff and/or providers. Alternatively, the “healthy” infants might be sicker or have more complicated health needs that are not measured by the maternal health conditions or infant factors included in the current risk adjustment. (Note that infants admitted to the NICU and those born at <37 weeks or <2500 g are excluded from this study.)

The level 1 hospitals had less variation in formula supplementation, which remained unchanged after risk adjustment, suggesting that the maternity care practices and the hospital breastfeeding culture at level 1 hospitals may be more consistent, more supportive, and/or better at deterring unnecessary, nonmedically indicated formula supplementation. Level 1 hospitals tend to be smaller community hospitals with fewer deliveries per year. They are rarely teaching hospitals and are less likely to have residents or medical or nursing students. As such, mother-infant dyads tend to have fewer interruptions or separations for resident or student teaching, and mother-infant dyads spend more time rooming-in.52,53 The number of interruptions has been negatively correlated with the frequency of breastfeeding, maternal perceptions of breastfeeding success, and maternal satisfaction.52,53 Because of these concerns and the recognition that separating mothers and infants can adversely impact breastfeeding success, recent recommendations call for providers to conduct newborn examinations and screening tests in the patient’s room to reduce maternal-infant separation time,54 and to limit visiting hours except for the mother’s primary support person.

This study has some limitations. Maternal demographic information is self-reported; however, authors of a previous study found that birth records include good quality maternal demographic data.55 Information was not available concerning the mother’s planned feeding intentions, her requests for formula, or the reasons why the infant was supplemented with formula. Information concerning maternal health conditions before and during pregnancy were provided, but information about the mother’s clinical course after birth was not available. Information about the infant was limited to his or her birth size, gestation, and admission to the NICU. Clinical conditions among term infants not admitted to the NICU that might require formula supplementation are limited and should be no more than 14.2%. Unless their prevalence differed significantly between hospitals within the same perinatal care level, clinical conditions would not impact the variation or relative ranking of hospitals.

This study, however, has many strengths. First, we used a large data set that includes the entire newborn population of a large, diverse state. Much of the information was reported on the birth certificate by hospital staff, including infant feeding and breastfeeding. The maternal demographic information is self-reported on the birth record, which has been shown to be of good quality maternal demographic data.55 Each mother also self-reported her race and ethnicity, which is more accurate than staff observations and is the recommended method for collecting racial and ethnic data.56 The analyses included many known risk factors for formula supplementation. The analyses were stratified by hospital level of perinatal care, which resulted in more homogeneous populations regarding maternal and infant clinical risk factors and hospital characteristics within each stratum. We designed the hierarchical modeling method to adjust for random effects at the hospital level, and the final models were a good fit in predicting the data with area under the curve ∼0.80.

Additional research is needed to understand why healthy breastfed newborns are supplemented with formula, and whether maternal requests for formula and how they are handled differ across hospitals or among patient populations. A better understanding of why level 1 hospitals are more likely to have low percentages of formula supplementation than higher-level perinatal hospitals is needed. The factors (eg, maternal, family or community characteristics, hospital leadership or staff knowledge, attitudes or behaviors, or hospital breastfeeding culture) that contribute to less formula supplementation at exemplar hospitals need to be identified by using positive deviance or other approaches. In addition, once best practices or strategies are identified, translational research is needed to increase their adoption to help reduce nonmedically indicated supplemental formula feeding, increase exclusive breastfeeding, support longer breastfeeding duration, and improve maternal and infant health outcomes.

Conclusions

We have found a wide variation in hospital-specific formula supplementation percentages, even when hospitals are stratified by level of perinatal care. There were hospitals at each of the 4 levels of perinatal care that met the HP2020 objective for limiting early formula supplementation (ie, ≤14.2%). Most of the variation in formula supplementation across hospitals was not accounted for by patient characteristics known to affect breastfeeding, such as SES or maternal or infant risk factors. To improve public health breastfeeding outcomes, a better understanding of the hospital, maternal, or community factors contributing to the disparities in formula supplementation is needed.

FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.

FUNDING: Support for this project was provided by the Robert Wood Johnson Foundation’s Public Health Law Research program (grant 12-069) and the New York State Department of Health. These findings do not necessarily represent the views of the funders.

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

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